643678787 has 2 divisors, whose sum is σ = 643678788. Its totient is φ = 643678786.

The previous prime is 643678753. The next prime is 643678843. The reversal of 643678787 is 787876346.

It is an a-pointer prime, because the next prime (643678843) can be obtained adding 643678787 to its sum of digits (56).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643678787 is a prime.

It is not a weakly prime, because it can be changed into another prime (643678727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321839393 + 321839394.

It is an arithmetic number, because the mean of its divisors is an integer number (321839394).

Almost surely, 2^643678787 is an apocalyptic number.

643678787 is a deficient number, since it is larger than the sum of its proper divisors (1).

643678787 is an equidigital number, since it uses as much as digits as its factorization.

643678787 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9483264, while the sum is 56.

The square root of 643678787 is about 25370.8255088399. The cubic root of 643678787 is about 863.4219111606.

The spelling of 643678787 in words is "six hundred forty-three million, six hundred seventy-eight thousand, seven hundred eighty-seven".